1. Field of Invention
This invention concerns apparatus and method for selectively monitoring the light intensity emitted from an oil-burner flame for purposes of determining when the burner is in need of preventative maintenance. More specifically, the apparatus aspect of the invention features: a sensor for sensing burner, flame-light intensity; a comparitor for tracking light-intensity drift over time relative to predetermined upper and lower limits; a display for indicating the need for burner maintenance; and a discriminator for selectively coupling out-of-range, intensity indications to the display. The method aspect of the invention features steps for: continuously sensing burner, flame-light intensity; comparing sensed, flame-light intensity to predetermined range limits; and selectively coupling out-of-range, intensity indications to a display for indicating the need for burner maintenance.
2. Prior Art
For some time now, the oil-heating industry and government have been working to further improve the efficiency of oil heating for both residential and commercial applications. While oil heating has shown itself to be cost efficient, reliable and safe, thus providing substantial value to its user, proponents of oil heating have sought to further increase its attractiveness by reducing wasteful oil consumption and increasing cleanliness of combustion.
In this regard, researchers have found that one of the principal indicators of combustion inefficiency and waste is smoke. As might be expected, production of smoke by the burner flame indicates the fuel being supplied to the system is not being completely combusted, with the result that less heat is being generated per pound of fuel consumed. Further, as smoke is produced, it accumulates on the heating system components; as for example, the system heat exchanger which, depending on the system type, transfers heat from the burner flame to either hot water or hot air. Accordingly, what heat the inefficient combustion is able to produce is less efficiently transferred from the flame, thereby, additionally diminishing the overall, energy-conversion efficiency of the heating system.
While in most cases the conditions that cause combustion inefficiency and associated smoke symptoms; for example, improper burner mixture settings, fouled oil injector nozzles or air intake openings, etc., can be readily corrected with a simple burner service call, most such situations go wholly unnoticed. Typically, system operators, usually home owners, are unaware of burner status and have occasion to call for service only when operation has so deteriorated that the burner stops working altogether. The consequence is that where home owners fail to recognize the condition of their heating systems, not only will they be penalized with the unnecessary costs of inefficient fuel consumption, but also, they will have to bear the expense of repairs for correcting soot-fouled equipment that results from inefficient operation, an expense which can add substantially to heating bills.
In the late 1980's researchers in the oil heating industry working under Federal sponsorship recognized this problem and proposed a simple, flame-quality monitor for indicating to home owners when burner operation had so deteriorated as to require maintenance for corrective action. Regrettably, however, while the system proposed suggested promise for at least diminishing the severity of the problem, it was found susceptible to practical limitations which rendered its operation commercially unattractive.
More specifically, Butcher et al. in U.S. Pat. No. 5,126,721 describe a flame-quality monitor for use in common, home-heating equipment. As noted by Butcher et al., burner deterioration resulting from improper mixture settings as well as other causes could be readily detected by: sensing flame light intensity in the visible band with a low-cost, cadmium-sulfide (CAD) photocell; comparing the sensed flame intensity to reference intensities using comparator circuitry; and noting the need for a service call with an indicator lamp provided at a display panel when the flame intensity moved out of an acceptable range. In accordance with the Butcher et al. design, the CAD photocell is mounted at the burner head, proximate the burner flame and supplies signals corresponding to the flame-light intensity to the electrical-comparator circuit located in a monitor box mounted on the burner housing. The comparator circuitry, in turn, provides an output signal to an indicator lamp at the display panel on the monitor box when the flame-light intensity goes above or below preset limits.
As noted, however, though the Butcher et al. monitor appeared to be a convenient, low cost approach to the problem of notifying home owners of degraded burner conditions, it was found susceptible to practical problems. Specifically, because of its simplistic design, the Butcher et al. monitor was found prone to giving false indications of burner degradation. As a result, when faced with an indication for service, users would be uncertain as to whether the monitor was correct or not. In effect, due to the potential for error, the monitor's credibility was undermined, and its commercial usefulness compromised.
The cause of the problem arises from the Butcher et al. approach to monitoring burner operation. Particularly, for the sake of simplicity, the Butcher et al. monitor does not discriminate between burner firings. Rather, it senses flame intensity each and every time the burner is activated. The difficulty with this is that in a conventional, home-heating system, the burner is repeatedly turned on and off for both heating and so called "standby" cycles. In standby cycle, however, the burner is on for only a short time to merely compensate for system losses, and accordingly, the system typically does not attain the operating temperature realized in the seasonally variably, but nonetheless, much longer space and/or water heating cycles. As a result, flame intensity measurements made during standby and short heating cycles are unreliable and susceptible of inaccurately indicating burner status.
As a result, experience has shown, that where no effort is made to discriminate between burner firings, a significant number of need-for-maintenance indications will be spurious. Accordingly, potential users; e.g., home owners who might purchase the monitor, are likely to encounter uncertainty and dissatisfaction on finding, after having incurred the cost of a service call, that the monitor indication was wrong.